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20/05/2024

Work of an ETO on ships with cranes. What most often breaks on cargo cranes?

Greetings! In this article, we will look at general issues related to the work of an ETO on ships with cranes.

Work of an ETO on ships with cranes. What most often fails on cargo cranes?

Recently, the number of ships with cargo cranes in the world merchant fleet has been increasing, so this article will be of interest primarily to ETOs who are just starting to work on such vessels.

A cargo ship performs, among other things, two important tasks - unloading, loading and transporting cargo. All these tasks involve an ETO, who is assigned more of a repair role than an operation one.

During cargo operations, the electroengineer must be in the standby mode, always be ready to repair or provide technical support to crane operators.

Manipulators (joysticks) for crane control
Manipulators (joysticks) for crane control
Preparing the crane for operation with joysticks
Preparing the crane for operation with joysticks

A marine electrician must be able to fully operate a crane. Because knowing the nuances of how a crane operates allows you to quickly troubleshoot problems.

Preparation for cargo operations

Timely inspection of the crane makes it possible to identify problems that may subsequently occur during cargo operations. First of all, you need to start with indoor and outdoor lighting, it must be in working condition. If possible, it is necessary to check the operation of all protections, limit switches and emergency operating modes of the crane.

Main motor of cargo crane hydraulics
Main motor of cargo crane hydraulics

Below are tips to help electrician prepare for cargo operations.

Tips for an electrician!

  1. Study the circuit diagrams (especially protection and interlock circuits) in advance.
  2. Each cargo crane (inside starter panels) must contain a schematic diagram and operating instructions.
  3. An electrician should always have on hand a bag with the necessary tools (up to hex keys of the required sizes, for example, for calibrating limit switches), instruments (multimeter), jumpers, electrical tape, etc.
  4. Always have the keys for blocking the limit switches (bypass) with you (if such are provided for the operation of the crane).

Schematic diagram of the operation of a cargo crane
Schematic diagram of the operation of a cargo crane

It is worth noting that for different vessels there may be different nuances of preparation, but often the above tips should be suitable for any vessel with cargo cranes.

Main contactors for starting the main motor
Main contactors for starting the main motor

The main contactors (starters) of electric motors of cargo cranes must be periodically cleaned of burnt deposits. Due to excessive burnt deposits and uneven contact contacts of the starters, the thermal protection may be tripped.

Oil cooler for hydraulics
Oil cooler for hydraulics
Thermal resistance sensor (detecting hydraulic oil temperature)
Thermal resistance sensor (detecting hydraulic oil temperature)
Checking brushes, rings and sliding contactsChecking brushes, rings and sliding contacts
Checking brushes, rings and sliding contactsChecking brushes, rings and sliding contacts
Checking brushes, rings and sliding contacts

Each cargo crane has a brush apparatus with sliding contacts, which also need to be maintained: cleaned, tightened and measured insulation resistance. This is a very important link in any crane that requires increased attention from the electroengineer team.

Crane maintenance

  1. Limit switches, especially outdoor ones, must be carefully greased and tested in operation.
  2. Oil coolers for cooling hydraulics must be cleaned of dirt. Otherwise, the fan motors will not cool down the hydraulic oil. As a result of dirty cooler, the fan first will trip, then the hydraulics trips due to high oil temperature.
  3. Air and oil filters must be in good condition.
  4. The oil level in the expansion tanks must be within acceptable limits, taking into account the operation of the crane.

Limit switch for rope break on a crane
Limit switch for rope break on a crane
Limit switches for protection of the cargo crane
Limit switches for protection of the cargo crane

Each cargo crane has a block of limit switches that protect the crane from damage and the rope from breaking. These limit switches must be checked periodically (usually every three months).

Limit switches
Limit switches operation settings

After each replacement of ropes on a cargo crane, it is necessary to recalibrate all limit switches according to the table from the manufacturer.

Fan and oil cooler of the hydraulic system
Fan and oil cooler of the hydraulic system

Crane breakdowns

The most frequent breakdowns of cranes are primarily related to protection and operation systems. This includes limit switches, push buttons, switches, keys, relays, and automation units.

  • The limit switches most often fail when installed externally. The main reason: aggressive work environment (moisture, salt).
  • Push buttons fail during operation.
  • The keys and mode switches of the crane also fail during operation.
  • Time relays and thermal relays. They can fail faster than conventional relays and contactors due to a more complex operating mechanism and, accordingly, a shorter service life.
  • Automation units fail most often due to overheating of the internal parts of the cargo crane (poor ventilation).

Malfunction of the time relay for starting the crane hydraulic motor (star-delta switching)
Malfunction of the time relay for starting the crane hydraulic motor (star-delta switching)

Working with grabs

There is also a trend in the fleet to increase bulk carriersbulk carriers with grabs, which may have chain, electric (cable or radio) systems for opening and closing the grabs. The work of grabs and their frequent breakdowns will be written in a separate article.

Grab on a ship
Grab on a ship
Operation of cargo cranes with grabs on a ship

Also I recommend to read articles about cargo crane breakdowns:

  1. Problems with cargo cranes. Some problems with cargo cranes that occur on the ship
  2. The cargo crane does not slew. Troubleshooting
  3. The crane hook goes up slowly. The cargo crane is not working. Troubleshooting
  4. PLC failure. The cargo crane does not start. Troubleshooting
  5. Motor Fault on the crane. Troubleshooting
  6. The crane jib is luffing down under its own weight. Troubleshooting
  7. Temperature controller. Replacing and adjusting the temperature controller on a cargo crane

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